How must Samba be configured, so that it can check passwords against the ones in /etc/passwd and /etc/shadow?

How must Samba be configured, so that it can check passwords against the ones in /etc/passwd and /etc/shadow?

A.
Run smbpasswd to convert /etc/passwd and /etc/shadow to a Samba password file.

B.
Set the parameters "encrypt passwords = yes" and "password file = /etc/passwd".

C.
Delete the smbpasswd file and create a symbolic link to the passwd and shadow file.

D.
Set the parameters "encrypt passwords = yes", "password file = /etc/passwd" and "password algorithm = crypt".

E.
It is not possible for Samba to use /etc/passwd and /etc/shadow.